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The network is the computer.
- Sun Microsystems Motto
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
2
Computer Networks
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History
Technology
Issues
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
3
Early Computer Networks
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Early machines were stand-alone
machines.
But people wanted to…
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share data
– share resources
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Growth
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1960s: some mainframes
– 1980s: personal computers at home
– 2000s: everything? mandatory?
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
4
ARPANET
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1969
The DOD wanted a network that could
handle computers that crashed
regularly.
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
5
Internet
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1983
ARPANET, CSNET & other networks
combined to form the Internet.
Network of independent, heterogeneous
networks.
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Within your network, use whatever protocol
you want.
– On the Internet, use TCP/IP
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
6
Vinton Cerf (1943- )
TCP/IP
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1973
Co-invented with Robert Kahn
TCP/IP – a suite of protocols, including:
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Transmission Control Protocol
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Internet Protocol
Together, they form the basis of the internet.
Image from www.elseviar.com
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
7
Growth of the ARPANET
ARPANET GEOGRAPHIC MAP, 1969
© Keith
Vander Linden, 2005,
Images from
www.cybergeography.org
Jeremy D. Frens, 2008
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Growth of the Internet
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
9
Distributed Network
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No one computer is in charge of the
Internet.
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All computers are in charge!
– Some take on more responsibilities.
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Computers are connected to each other
in multiple ways.
Each computer routes data closer to its
destination.
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Routers: extra routing responsibilities.
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
10
Packet Switching
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Data is split up into small packets.
Each packet is sent on its own to a
nearby computer.
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Not all packets take the same route!
The packets are reassembled into the
original data.
If a packet goes missing, it’s resent.
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
12
Network Architectures
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Networks can be characterized by how
they manage their resources.
Common network architectures:
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Server1
Client-Server
Server2
Network
User Client1
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Peer-to-Peer
User Client2
peer
User Client3
peer
Network
peer
peer
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
13
Network Technologies
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Copper wire
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coaxial or twisted pair (telephone wire,
cat5/ethernet cable)
Fiber-optics
Wireless technology
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Radio Frequency (RF)
– Infrared radiation
– Microwave
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
15
Network Architecture
The rest of
the Internet
Calvin
100 Mbps each
SB 372
ResNet
US
Signal
(ISP)
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
16
Calvin’s Network
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Dual 100 Mbps fiber connections to/from
US Signal
400 switches
Distribution closets in all buildings – with
big one in Bolt-Heyns-Timmer
All data through a “packet shaper”,
“intrusion prevention device”, and “external
firewall”.
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
17
Calvin’s Network
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
18
Internet Services
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The Internet supports a variety of
information services.
These services use the Internet.
Examples:
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World Wide Web (http)
– Email
– Telnet/SSH
– FTP/SFTP
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
22
Inclusiveness of the Web
What’s the
Big Idea
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How “world-wide” is the web?
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How could we make it more international?
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How inclusive or intrusive should it be?
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
23
Malware
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malicious software: “software to infiltrate a
computer system without the owner’s
informed consent” [wikipedia]
definition based on the user’s intent or motive
– Note: God judges us based on our motives.
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includes computer viruses, worms, trojan
horses, rootkits, spyware, dishonest
adware, crimeware, etc.
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
24
Malware (cont)
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virus: attached to an existing program,
does damage to files, and copies itself.
worm: unattached, damages the network,
and copies itself.
trojan horse: opens up a “backdoor” to the
system for future unauthorized access;
non-replicating.
spyware: collects info about users.
crimeware: for identity theft.
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008
25
Privacy and the Internet
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The internet never sleeps, it never forgets
and it doesn’t always tell the truth.
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What’s the
Big Idea
phishing schemes
The internet makes information more
vulnerable to improper use.
What can be done about this?
“…be shrewd as snakes and as innocent
as doves.” - Matthew 10:16
© Keith Vander Linden, 2005,
Jeremy D. Frens, 2008